Water conducting household device having desalination device and related method

ABSTRACT

Apparatus for treating laundry as the items to be washed includes a container for the items to be washed. The container is in fluid communication with a water supply system. Connected to the water supply system is a desalination apparatus for producing desalinated water having a conductivity of less than 200 μS/cm, with the desalination apparatus being constructed as an ion exchanger. A reservoir is connected to the desalination apparatus for storing water with a higher salt concentration for later use.

The invention relates to a water-conducting household appliance having a desalination apparatus, as well as a method for treating items to be washed in a water-conducting household appliance.

When treating dirty laundry in a washing machine the actual wash step using suitable detergents is generally followed by a rinse phase comprising one or more rinse steps using water. In this rinse phase the wash liquor containing dirt and detergent and any residues of dirt and detergent adhering to the laundry items are eliminated from said laundry items. With the known methods the quantity of such substances remaining on the fibers of the laundry items is smaller, the more water is used for rinsing and/or the more frequently rinsing is performed using water. There is however a need to reduce the time allowed for the rinse phase and the quantity of water used for rinsing based on the demands of washing machine users and with a view to protecting the environment. At the same time requirements relating to the wash efficiency of a washing machine are becoming more demanding.

Water softeners to make the fresh water used “softer” are already the prior art in dishwashers. Water softening is understood to be the elimination of the natural alkali cations Ca2+ and Mg2+ dissolved in the water, which reduce the washing action of washing agents due to the formation of calcium soaps and can cause problematic scale deposits in pipes and appliances. Soft water is produced from what is commonly referred to as hard water.

The elimination of just calcium and magnesium ions from the water, as occurs in dishwashers, would not be sufficient in a laundry wash procedure to improve rinse efficiency perceptibly. What are known as chemical water softeners are therefore frequently added to washing agents to interact significantly with the natural alkali cations, which are then no longer available to produce problematic reactions. In this process the natural alkali cations are not eliminated from the water. The water now behaves to a certain extent as if it were soft water. This process is therefore not an actual softening and the disadvantages of hard water essentially continue to be present. The water softener also has to be eliminated during the rinse cycle, thereby driving the quantity of rinse water required still higher.

DE 19 44 397 A describes a washing machine or dishwasher having a water softening facility that operates according to the reverse osmosis principle, having at least one semi-permeable film, one surface of which is assigned to a water supply line and the other surface of which is assigned to a water drain line. The drawing shows a dishwasher, in which a storage container with a drain valve can be provided for softened water.

DE 197 09 085 A describes a method for washing laundry, in particular in a household washing machine, wherein the laundry is treated with wash fluid in a tub during a wash segment and with rinse fluid during subsequent rinse segments and wherein at the end of the respective wash/rinse segment the tub is emptied, the wash fluid and/or rinse fluid of at least one rinse segment being emptied into a collector and being re-used after preparation by means of a reverse osmosis, micro, ultra or nano filtration procedure while buffered in a reservoir. The prepared wash or rinse fluid is supplied for a later rinse segment of the same program sequence.

DE 296 11 091 U describes a fluid-conducting household appliance having a program controller, wherein the further program sequence can be set as a function of detected measurement variables, at least one conductance sensor being provided to determine the conductance of a fluid present in the region of action of the household appliance.

The object of the present invention was therefore to provide a water-conducting household appliance with reduced water consumption and a method for reducing water consumption in a water-conducting household appliance.

According to the invention this object is achieved by a water-conducting household appliance having a container for items to be washed, a water supply system and a drain system, a program controller, a desalination apparatus for producing desalinated water and a rinse water reservoir, the desalination apparatus being an ion exchanger. Advantageous embodiments are embodied in the features of the corresponding dependent claims, which can be used individually or in combination.

This has the advantage that water consumption can be reduced, in particular during rinsing when added treatment agents are to be eliminated.

The water-conducting household appliance of the present invention is preferably a washing machine or a washer-dryer but it can also be a dishwasher. All water-conducting household appliances according to the invention comprise a container for items to be washed, i.e. for example the interior of a dishwasher or a tub with a laundry drum located therein in the case of a washing machine. The items to be washed that are referred to can be any items to be treated that can be treated in an inventive water-conducting household appliance, so laundry in the case of a washing machine.

The inventive water-conducting household appliance furthermore comprises a program controller to control the programs to be performed. The program controller is preferably connected to a display facility which can additionally also comprise input facilities for the inputting of data by the user.

The term washing machine is used in the following to represent the water-conducting household appliance.

The softened water referred to in the introduction should not be confused with distilled or demineralized water. Demineralized water, also referred to as deionized or fully desalinated water is water (H2O) without the minerals (salts, ions) occurring in normal spring and tap water. Conductivity is measured to determine the degree of purity of a demineralized water. Conductance meters are used for this. Conductivity is given in S/m (siemens per meter). Since demineralized water has a very low conductivity, the usual unit is mS/m or in technical parlance μS/cm. Tap water has a conductivity of 700 to 800 μS/cm depending on water hardness. Even softened water is still around 600 μS/cm. The value for desalinated water depends on the manner of desalination and is generally below 200 μS/cm. Since, chemically speaking, water is an ampholyte, which can react with itself, even the purest water has a low electrical conductivity: arithmetic threshold 0.055 μS/cm at 25° C. The value for distilled water is between 0.5 and 5 μS/cm.

For the purposes of the present invention, desalinated water within the meaning of the invention means water having a conductivity of less than 200 μS/cm, preferably less than 100 μS/cm, more preferably less than 50 μS/cm, even more preferably less than 20 μS/cm. Fully desalinated water with a conductivity of less than 10 μS/cm is particularly preferred.

This degree of desalination is achieved by providing a desalination apparatus in the machine. The desalination apparatus is preferably connected to the fresh water supply. It can be located upstream of the intake facility or past this.

In the inventive water-conducting household appliance the desalination apparatus is an ion exchanger.

Therefore with the inventive method an ion exchanger is particularly preferably used as the desalination apparatus. The ion exchanger is not particularly restricted according to the invention. However a synthetic resin ion exchanger, in particular a mixed-bed ion exchanger, is preferably used. The ion exchanger can be located in a suitable cartridge (in the following also referred to as the ion exchanger cartridge), which has intake and drain connections. The insertion of such a cartridge into the washing machine and the removal of the cartridge can take place by way of a suitable opening and support apparatus in the washing machine. For example such a cartridge can engage with corresponding intake and drain connections of the washing machine.

In another embodiment a reverse osmosis facility is provided as the desalination apparatus. A reverse osmosis facility is a facility, which, in a physical membrane filtration procedure referred to as reverse osmosis, allows a building up of the concentration of substances dissolved in fluid, by reversing the natural osmosis process by means of pressure. This allows water to be desalinated with almost no maintenance. There is no need for an exchange or regeneration process. However because the pressure has to be set for example, the structure of an efficient reverse osmosis facility is expensive in terms of energy consumption and cost. Also the waste water has a higher salt concentration.

The desalination apparatus can also be an electrodialysis facility. Electrodialysis is also a desalination method known per se without major maintenance outlay.

If a by-product of desalination is water with a higher salt concentration (as is the case with reverse osmosis for example), this can also be stored and then used in one of the first rinse cycles in a later wash procedure. This has the advantage that substances that are active in the wash process are bound to a greater degree by the salts and can be rinsed out in particle form. To this end the inventive washing machine has a reservoir, which is connected to the desalination apparatus and from which the water with a higher salt concentration stored therein can then be supplied again by way of corresponding lines to the tub. Its supply is likewise controlled by way of the program controller.

In one preferred embodiment of the invention the washing machine contains a first sensor for determining the functional capacity of the desalination apparatus. A sensor for registering the presence of the cartridge in the washing machine can be provided for example.

Preferred in terms of the invention is a first sensor, which is disposed expediently downstream of the desalination apparatus, preferably between the desalination apparatus and the tub, and measures the salt content of the water exiting from the desalination apparatus. The first sensor can in particular be a sensor for the direct or indirect detection of ions. An ion-selective electrode or a conductivity sensor for example is suitable. A conductivity sensor generally comprises two electrodes disposed in a fluid to be tested, such sensors providing information about the qualitative and quantitative presence of different substances such as salts, detergents or fabric conditioners by way of the conductivity measured between them. According to the invention the first sensor preferably comprises a conductivity sensor.

The first sensor is preferably connected to the program controller and can thus be used to monitor a desalination capacity of the desalination apparatus. In this process the first sensor measures a salt content L in the water leaving the desalination apparatus and compares the measured salt content L with a predefined upper limit value L(max) stored in the program controller for example. When L(max) is reached or exceeded it is preferably possible to indicate exhaustion of the desalination capacity of the desalination apparatus. When the desalination capacity of the ion exchanger cartridge dwindles, the conductance of the water leaving the cartridge registered by a first sensor in the form of a conductivity sensor for example increases. The need to replace the cartridge can then be displayed acoustically or optically by way of a display facility of the washing machine. According to the invention provision can also be made for a laundry treatment procedure to be performed despite the absence of an ion exchanger cartridge or an exhausted ion exchanger capacity.

A second sensor can also be provided, which is disposed in the container for items to be washed, i.e. in the tub in a washing machine, and measures a content S of inorganic and organic substances in the fluid present there and compares the measured content S with a predefined value S(min). The program controller ensures that when the content reaches or drops below S(min) the water supply is terminated and/or no further rinse steps are performed. The second sensor is preferably an optical sensor, a tensiometer or a conductivity sensor. An optical sensor measures optical properties of a fluid, which differ for water and water containing inorganic and/or organic substances. Correspondingly the presence of inorganic and/or organic substances in an aqueous solution can be determined qualitatively and quantitatively. A tensiometer is a simple, dynamic measuring system for determining the content of surface-active substances in a fluid. A signal proportional to the surface tension of the fluid is generated according to what is known as the bubble pressure method using the tensiometer, said signal corresponding to the concentration of surface-active substance. An optical sensor or a conductivity sensor is particularly preferably used as the second sensor. In one preferred embodiment of the inventive method when a conductivity sensor is used it is also used for foam detection. The second sensor is preferably located in the lower region of the tub.

For a quantitative determination of the salt or inorganic and organic substance content data stored as required in a memory of the program controller can be used to establish the relationship between the nature and concentration of the salts or inorganic and organic substances and the signal from the respective sensor (e.g. conductivity, surface tension, optical characteristics).

According to the invention an exhausted desalination capacity of the desalination apparatus, i.e. the presence of salt in the water to be used, is preferably indicated before contact with the laundry items to be rinsed, in the form of an optical and/or acoustic signal. The same applies to an indication of the elimination of inorganic and organic substances in the rinse water in the tub to below a tolerable content. An acoustic display facility for example could be used for this purpose, e.g. one or more buzzers with different sounds or tones, or a voice synthesizer with messages such as “Regenerate ion exchanger” or “Rinse terminated”. Corresponding qualitative and quantitative information about the presence of salts in the water or inorganic and/or organic substances in the rinse water can also be provided by way of an optical display facility (LED or LCD).

The inventive washing machine therefore preferably has a display facility for displaying the presence of condition L greater than/equal to L(max) and/or the condition S less than/equal to S(min), where L is the quantity of salt L measured by a first sensor, S the quantity of inorganic and organic substances measured by the second sensor, L(max) a predefined quantity of salt and S(min) a predefined quantity of inorganic and organic substances. The analysis of the measurement values supplied by the first and/or second sensor and the evaluation of the salt, inorganic and/or organic substance content of the rinse fluid and an optionally resulting regulation of the water supply in respect of the quantity of water and the number of rinse steps are preferably performed by a program controller of the washing machine.

To save more water the used rinse water can be re-used. To this end a rinse water reservoir is provided, in which the used rinse water is buffered so that it can be re-used for example in a subsequent wash cycle. The used water from the last rinse cycles in particular is so clean that it can be used as it is instead of fresh water for wetting and washing. Already desalinated, used rinse water also has the advantage that the concentration of washing agent does not have to be adjusted in respect of hardness, as the desalinated water is already “soft”, even after it has been through a rinse cycle according to the invention. The used desalinated water is therefore even more advantageous as washing water than fresh water.

A further subject matter of the present invention is a method for treating laundry in a washing machine comprising a laundry drum, a tub, a water supply system, a wash liquor drain system having a drain pump, a program controller, a desalination apparatus for producing desalinated water and a rinse water reservoir, the method comprising at least one wash step and at least one rinse step, with desalinated water being used in a rinse step and the desalinated water used in the rinse step being buffered and re-used in a later wash procedure.

Generally in the method for treating laundry the actual wash phase is followed by a rinse phase, which consists of one or more rinse steps with water, generally two to three rinse steps. According to the invention desalinated water can be used in any of these rinse steps. The inventive method is preferably not performed in a first rinse step but in a second and particularly preferably in one of the last rinse steps. The quantity of salts and other substances to be eliminated from the laundry items decreases with each rinse step so desalinated water can be used particularly efficiently when the quantity of salts and other substances to be eliminated from the laundry items has already significantly decreased.

Water with the normal salt concentration for tap water is generally adequate for a first rinse step, so any additional effect due to the use of desalinated water during the first rinse is relatively minor. In contrast a positive effect can be achieved even by using water with a higher salt concentration than tap water (e.g. as a result of desalination using reverse osmosis), since the substances that are active in the wash process can be bound to a greater degree by the salts.

In one preferred embodiment desalinated water is used in the penultimate rinse step. This is followed by a fabric conditioner adding step. A fabric conditioner adding step according to the present invention is a rinse step in which it is possible to add further substances to the items being rinsed, e.g. a fabric conditioner, an impregnation means, fragrances or the like. Since these substances are to remain on the laundry, no further rinse steps are performed after this.

The signals from the first and/or second sensor can be measured continuously or non-continuously during the inventive method. For example the measurement by a first sensor can be performed at the start of a rinse step and the measurement by a second sensor can be performed after the supply of water to the tub has been terminated.

When the content reaches or drops below S(min) the water supply is preferably terminated and/or no further rinse steps are performed. The quantity of water to be used in a rinse step is generally a function of the laundry load size in the washing machine. The load size can be determined by a measure known per se. As a result the rinse phase can be matched very precisely to the predefined load. A quantity of water of approx. 15 to 18 1 is generally required in a rinse step for a 5 kg laundry load. When the inventive method is performed, this quantity of water and/or the number of rinse steps to be performed is/are reduced. The rinse action of the inventively desalinated water can be improved further according to the invention by establishing a slightly acid pH value in the desalinated water, for example by adding an acid.

According to the invention the desalinated water used in a rinse step is stored and re-used in a later wash procedure, e.g. in the next wash cycle. The advantage here is that the required quantity of washing agent only has to be dosed according to the soiling of the laundry, without taking account of water hardness, since the water has already been desalinated. The salts and substances absorbed again in the last rinse cycle are present in such small concentrations that the wash process is not impaired.

The invention has numerous advantages. The inventive method has the advantage that the quantity of rinse water required generally for the rinse phase can be significantly reduced whilst maintaining the rinse effect that can be achieved by normal rinsing. This is advantageously possible for the entire laundry treatment in the washing machine without extending the duration. In certain embodiments the invention also allows the exposure of the laundry to unwanted salts and other is inorganic and/or organic substances to be reduced. In other words the use of fabric conditioners can be reduced or avoided.

The invention is illustrated in more detail in the following based on FIG. 1.

FIG. 1 shows a schematic diagram of a front sectional view of an inventive washing machine.

The schematic diagram in FIG. 1 shows the parts of a washing machine, in which a method to be described in the following is performed, that are of relevance in the present instance. Other embodiments are conceivable. The washing machine has a container 1 for the items to be washed 7, in this instance the tub 1, in which a laundry drum 2 can be supported rotatably and operated by a drive motor 14. The flow of wash liquor 6 or rinse water 6 through the laundry 7 is intensified by interaction with specifically shaped agitators 4 and scoops 5 for the wash liquor 6. The washing machine has a wash liquor supply system, which comprises a water connection for the domestic water supply network 8, an electrically controlled valve 9 and a supply line 10 to the tub 1, which passes by way of an intake tray 11, from which the intake water (fresh water) can transport treatment agents into the tub 1. A heating facility 13 is present in the tub 1. The valve 9 and the heating facility 13 can be controlled by the program controller 12 as a function of a program sequence plan. A sensor 15 is provided to measure the hydrostatic pressure p in the tub 1.

A desalination apparatus 17 is provided to desalinate water, being disposed in this embodiment between the intake valve and the tub, being also connected to the tub 1 however by way of a line past the intake tray. In one embodiment (not shown) the desalination apparatus 17 can also be provided between valve 9 and intake tray 11. It is however advantageous if the desalination apparatus 17 is disposed so that it does not have to be used to desalinate intake water every time water is supplied, since on the one hand the use of desalinated water is not absolutely necessary for washing and on the other hand desalination capacity can be conserved, if desalinated water is only supplied in certain program steps. As mentioned above, desalinated water should be used preferably during rinsing and particularly preferably at the end of the rinse procedure.

A first sensor in the form of a conductivity sensor 19 is present between the desalination apparatus 17 and the tub 1 to determine a salt content of the water routed through the desalination apparatus 17.

In the embodiment illustrated a reservoir 18 connected to the desalination apparatus 17 is additionally provided for water with a higher salt concentration. If the desalination apparatus 17 is a reverse osmosis facility, the water containing more salt produced during the desalination process is collected here and conserved for later use, e.g. for initial rinse cycles.

A further rinse water reservoir 22 is also provided in the illustrated embodiment, which can store the water used during rinsing. This water, particularly if it is the previously desalinated water used during rinsing, can then be used again for a later wash cycle. To this end the rinse water reservoir 22 is connected by way of a line 23 to the valve 9, which also controls the fresh water supply.

Located in the lower region of the tub 1 is a second sensor in the form of a second conductivity sensor. The second conductivity sensor 20 can be used to determine the inorganic and organic substance content of the rinse water after rinsing. To this end data stored in a memory of the program controller 12 can be used to establish the relationship between the nature and concentration of the salts or inorganic and organic substances and conductivity. 21 designates a display facility for indicating the presence of condition L greater than/equal to L(max) in the water to be used or condition S less than/equal to S(min) in the rinse water in the tub 1. After comparing a measured content S of inorganic and organic substances with a lower predefined value S(min) and ascertaining whether the content has reached or dropped below S(min), the water supply into the tub 1 and drum 2 of the washing machine is terminated and/or no further rinse steps are performed.

LIST OF REFERENCE CHARACTERS

-   1 Container for items to be washed, tub -   2 Laundry drum -   3 Axis of rotation of drum -   4 Agitator -   5 Scoops -   6 Wash liquor -   7 Items to be washed, laundry -   8 Domestic water supply network -   9 Valve -   10 Supply line -   11 Intake tray -   12 Program controller -   13 Heating facility -   14 Drive motor -   15 Pressure sensor -   16 Pump -   17 Desalination apparatus -   18 Reservoir for water with a higher salt concentration -   19 First conductivity sensor -   20 Second conductivity sensor -   21 Display facility -   22 Rinse water reservoir -   23 Line 

1-11. (canceled)
 12. Apparatus for treating laundry as the items to be washed, said apparatus comprising: a container for the items to be washed; a water supply system in fluid communication with the container; a desalination apparatus, connected to the water supply system, for producing desalinated water having a conductivity of less than 200 μS/cm, said desalination apparatus being constructed as an ion exchanger; and a reservoir connected to the desalination apparatus for storing water with a higher salt concentration.
 13. The apparatus of claim 12, further comprising, constructed in the form of a washing machine or washer-dryer.
 14. The apparatus of claim 12, further comprising a first sensor for determining a functional capacity of the desalination apparatus.
 15. The apparatus of claim 12, further comprising a display facility.
 16. The apparatus of claim 12, wherein the display facility indicates a functional capacity of the desalination apparatus.
 17. A method for treating laundry in a washing machine, comprising: desalinating water in a desalination apparatus to produce desalinated water having a conductivity of less than 200 μS/cm; storing desalinated water for use in a rinse step in a rinse water reservoir for optional application in a later wash step; and storing water with a higher salt concentration resulting during desalination in a reservoir connected to the desalination apparatus for later use.
 18. The method of claim 17, wherein desalinated water is used in one or more of last rinse steps.
 19. The method of claim 17, wherein desalinated water is used in a penultimate rinse step which is followed only by adding a fabric conditioner.
 20. The method of claim 17, wherein the rinse step is a last rinse step.
 21. The method of claim 17, further comprising measuring a salt content in the water exiting from the desalination apparatus by a first sensor, comparing the salt content with a predefined upper limit value, and indicating exhaustion of the desalination apparatus when the predefined upper limit value is reached or exceeded.
 22. The method of claim 17, further comprising measuring in a tub a content of inorganic and organic substances in the fluid present there by a second sensor, comparing the content with a predefined value, and terminating the water supply or barring any further rinse step, when the content reaches or drops below the predefined value.
 23. The method of claim 17, wherein the water with a higher salt concentration stored in the reservoir is used for a rinse cycle in a later wash process. 